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Gene Expression

Teacher/Instructor Patrick Roisen
Patrick Roisen

M.Ed., Stanford University
Winner of multiple teaching awards

Patrick has been teaching AP Biology for 14 years and is the winner of multiple teaching awards.

Gene expression is the process of taking genetic information in DNA and translating it into biological functions such as protein synthesis. Gene expression explains the effect of genes on the body on both the macroscopic and microscopic level.

Gene expression is the way that a gene a section of your DNA is turned into the physical traits that you show in your body. So it's the process of how this happens, of how a gene is used to affect an organism's traits. It's how genotype, the type of genes you have influences your physical characteristics, your phenotype.

Now a lot of times this is what allows your genes to turn on or off based on what's going on in your environment. For example, most people are born with the ability to digest milk, lactose sugar. And that's because most humans are born and they're fed via breast milk. But most humans after about age two or three, stop drinking breast milk. And so in the majority of humans for most of the time most people would turn off the ability to digest lactose after they stop after they were weaned and stopped breast feeding. So that's an example of how a gene was expressed earlier on but later on in life it turns off. So that's an example of gene expression altering in response to the environment.

You know that as you age and go through puberty, certain genes that you had as a baby all of a sudden turn on and you start growing hair in places where you didn't have hair before, you start sweating a lot. All sorts of weird things happen. That's gene expression.

Now generally it involves protein synthesis because remember genes are sections of DNA that encode the instructions on how to build a protein. Now there's three basic strategies to follow in order to influence how much of a protein is present or how active a protein is. One is to increase the rate of transcription the copying of the DNA section. So you can increase it to have more of that protein to have more of that trait, or you can decrease the transcription. So you can slow down the creation of that protein so there's less of it.

Altering the mRNA that's being made during transcription. So you can cut out parts and that will create differences in how that gene is expressed. Or you can make that messenger RNA last for a shorter period of time or last for longer periods of time within the cell.

Last is altering or destroying the protein. That's not followed so much or used as much as the other two methods but it sometimes is a way to influence how a gene is being expressed by the overall organism is to destroy the protein faster or allow it to last longer than it otherwise would in the cell.

Now one of the things I really want to highlight on this is this is the idea that genes are predictions but not necessarily absolutes. If you have the genes for a particular trait, some traits you will show them. For example, I have the genes for having my arms attached up here on my shoulders. I expressed it. But I also have based on my family history perhaps genes that might make me more likely to get diabetes. I can alter that gene expression by altering my environment. If I stay off the sweets and I eat a healthy diet and exercise, chances are I won't express those genes. So this is something to think about in your life and this is one of the reasons why science and biology is so interesting and useful to learn about because it allows you to think about what's in your background? And whether or not you want to express it.